... Kepler Laws . ... Planets move around the Sun in ellipses , with the Sun at one focus . ... Kepler's laws describe the motion of planets around the Sun. ... The orbit of the Earth around the Sun. ... and third, he, proved that if the above two held, Kepler's laws could be derived mathematically..... but with one small change : planets orbited not around the Sun, but around a common center of gravity. ... The Earth's orbit, and most planetary orbits, are very close to circles. ... Kepler's 3rd Law . ...